珠江口盆地大地热流特征及其与热岩石圈厚度的关系

Characteristic of surface heat flow in the Pearl River Mouth Basin and its relationship with thermal lithosphere thickness

沉积盆地现今热流特征是岩石圈构造-热演化过程的综合反映和盆地热史恢复的必要约束条件,其总体变化趋势与热岩石圈厚度密切相关.本文根据新收集的珠江口盆地19口钻井温度数据,新增计算了19个大地热流数据,其中12个数据位于深水区(水深大于300 m),丰富了该盆地深水区钻井地热数据.结合前人研究成果,绘制了该盆地的大地热流图,并分析了其热流分布特征.在此基础上通过求解一维热传导方程,计算得到36口井位处的热岩石圈厚度,量化了盆地大地热流与热岩石圈厚度间的关系.结果显示,珠江口盆地大地热流值介于24.2~121.0 mW·m^(-2),平均71.8±13.6 mW·m^(-2),新增盆地深水区钻井平均热流值高达84.5±4.4 mW·m^(-2).大地热流分布整体上从陆架区到陆坡区升高,而热岩石圈厚度整体分布趋势与大地热流相反.大地热流与热岩石圈厚度间存在良好的指数相关性.

The characteristics of surface heat flow,which are the comprehensive reflection of lithospheric tectono-thermal evolution and a constraint on thermal history reconstruction,are of great importance for dynamics research and hydrocarbon resource assessment in sedimentary basin.19 new heat flow values have been calculated based on the newly collected temperature data of the Pearl River Mouth Basin,among which,12 heat flow data located in the deep water area（where water depth exceeds 300 m）.The new data,which could make better control on heat flow distribution of the basin,is of great value since the rarity of the borehole heat flow in the deep water area.Together with previous studies,a heat flow contour map of this basin has been depicted and the distribution characteristics have been further analyzed.The lithosphere thickness at 36 wells also has been calculated by solving the one-dimensional heat conduction equation and then its relationship with the surface heat flow has been acquired.The results indicate that the surface heat flow values of the Pearl River Mouth Basin vary from 24.2 to 121.0 mW ？ m^（-2）,with an average of 71.8 ± 13.6 mW ？ m^（-2）,and the average borehole heat flow in the deep water area can reach as high as 84.5 ± 4.4 mW ？ m^（-2）.The heat flow value increases from the shelf area to the slope area while the lithosphere thickness shows an opposite trend.The relationship between the surface heat flow and lithosphere thickness can be expressed by an exponential function.